The present invention relates generally to force measuring devices and, more particularly, to devices for measuring the force transferred from a driven element to a rotating, non-driven element such as a moving web and an idler roller.
There are a variety of processes wherein a moving web is driven through a system. Quite often these processes involve the production or coating of the moving web. Thus, the moving web is typically driven by a drive roller through a predetermined and often serpentine web path that may include one or more idler rollers. In order to control the process, it is often necessary to determine the force transferred from the moving web to an idler roller. Typically this measurement is currently made using a prony brake that utilizes a rope wrapped around an idler roller or drum and which can be operated only from inside the machine. Machines for the production of film base as well as machines used to sensitize film base are fully enclosed such that the environment within the enclosure can be controlled to facilitate various manufacturing operations such as curing or drying of web or emulsions. The enclosures also enable the recovery of solvents. The rope is attached to both ends of a spring scale with the aid of an alignment pulley. A first person pulls the spring scale in a direction to tighten the rope. As the roller starts to stall as determined by a second person operating a tachometer, the prony brake operator reads the force in inch-pounds.
In that many of the processes where it is necessary to measure the force transferred from the moving web to an idler roller are operated in enclosed environments such as the coating of photographic films, the prior art tool and method have serious shortcomings. The use of the prior art prony brake results in the interruption (an interruption is defined as any time a machine is running in a non standard mode) of various process conditions such as temperature, humidity, solvent loading, not to mention the effect on the process as a result of the loss of traction through the operation of the prony brake. Further, because many of the processes are operated in enclosed environments it is necessary for the operators of the prony brake and the tachometer to enter the closed environment thereby exposing the operators quite often to elevated temperatures and high solvent vapor concentrations often necessitating the use of cumbersome safety equipment.
It is therefore an object of the present invention to provide a device for measuring the force transferred from a driven web to an idler roller.
It is a further object of the present invention to provide a device for measuring torque between elements where one is driven (web) and one is idling (idler roller).
Yet another object of the present invention is to provide a means for determining the coefficient of friction between a driven web and an idler roller.
Still another object of the present invention is to provide a device for measuring torque on a rotating element imparted by a moving surface in contact with the rotating element.
Briefly stated, the foregoing and numerous other features, objects and advantages of the present invention will become readily apparent to those skilled in the art upon a review of the specification, claims and drawings set forth herein. These features, objects and advantages are accomplished by providing a tachometer coupled to a torque meter in an arrangement that includes a cantilevered drive shaft adapted to interface with a socket-head screw that captures a bearing mounted to an end of an idler roller. The socket-head screw capture bearing can extend beyond the enclosed environment of the operating process. In such manner, the operator of the device of the present invention can avoid exposure to the potentially hazardous process temperatures and gases. The tool includes a hand brake extending from the torque meter. A single person can operate the tool merely by inserting a cantilevered drive shaft into the bearing capture thereby causing the idler roller to drive rotation of the shaft of the torque meter and also the tachometer. The device can be operated by applying pressure to the hand brake allowing the operator to observe both the tachometer and the torque meter. When the operator sees a decrease in rotational speed as detected (indicating the web is slipping on the idler roller surface) by the tachometer, the operator merely needs to read the value of the force as detected by the torque meter at that point in time. It is this amount of force minus bearing losses that the moving web is transferring to the idler roller.